Kinetics of reduction of nitric acid by electrochemical method and validation of cell design for plant application

Employing electrochemical method, the concentration of nitric acid had been reduced from 4 to about 0.5 M, under constant current/potential conditions in batch mode, for the purpose of optimizing the process parameters for the destruction of nitric acid in radioactive liquid waste, with good energy efficiency. Based on the rate constants determined from the batch process, a cell assembly in cylindrical configuration was designed for the electro-reduction of nitric acid in continuous mode, in radioactive environment. The steady state concentration of the acid at the outlet was compared with that concentration calculated using model equation and the agreement between the two sets of data was found to be reasonable. Cyclic voltammetric runs were recorded to understand the reduction behavior of nitric acid on platinum electrode. The results revealed the reduction of nitrate ion to be a quasi–reversible process and for the scan rate of 0.1 V s−1, values of 3.3 × 10−6 cm2 s−1 and 1.37 × 10−3 cm s−1 were computed for the diffusion coefficient and heterogeneous electron transfer rate constant, respectively.